1. Field of the Invention
This invention relates to display monitors in computer systems, and more particularly to a method and apparatus of initialization and communication with a display monitor having both an analog and digital interface.
2. Description of the Related Art
Computer systems in general and personal computer systems in particular have attained widespread use for providing computer power to many segments of today""s modern society. A personal computer system can usually be defined as a desktop, floor standing, or portable microcomputer that includes a system unit having a system processor and associated volatile and non-volatile memory, a display monitor, a keyboard, one or more diskette drives, a fixed disk storage device and an optional printer. One of the distinguishing characteristics of these systems is the use of a system board to electrically connect these components together. These personal computer systems are information handling systems which are designed primarily to give independent computing power to a single user (or a relatively small group of users in the case of personal computers which serve as computer server systems) and are inexpensively priced for purchase by individuals or small businesses. A personal computer system may also include one or a plurality of I/O devices (i.e. peripheral devices) which are coupled to the system processor and which perform specialized functions. Examples of I/O devices include modems, sound and video devices or specialized communication devices. Mass storage devices such as hard disks, CD-ROM drives and magneto-optical drives and display monitors are also considered to be peripheral devices.
Computer systems, including personal computer systems, are increasingly using dual-interface display monitors. These dual-interface monitors have both a digital interface and an analog interface. The computer system, in order to correctly initialize and communicate with the display monitor, must have a manner of identifying which interface should be used. Traditional single-interface display monitors utilize a file conforming to a standard promulgated by the Video Electronics Standard Association (xe2x80x9cVESAxe2x80x9d(trademark)) to identify itself to the computer system. This standard is known as the Extended Display Identification Data (EDID(trademark)) Standard, with a modified version of the standard being referred to as the Enhanced Extended Display Identification Data (E-EDID(trademark)) standard. Both the EDID(trademark) and E-EDID(trademark) standards will be referred to herein collectively as xe2x80x9cthe EDID(trademark) standardxe2x80x9d or simply xe2x80x9cEDID(trademark)xe2x80x9d.
The EDID(trademark) standard defines a 128-byte data structure that is communicated from the display monitor to the processor. The EDID(trademark) data structure, sometimes referred to herein as an xe2x80x9cEDID filexe2x80x9d, is an identification file that is communicated over a communications channel. As used herein, the term xe2x80x9cEDID filexe2x80x9d refers to a data structure conforming to either the EDID(trademark) and the E-EDID(trademark) standards. The EDID(trademark) standard assumes that the information contained in the data structure defined by the EDID(trademark) standard will be communicated over a communications channel that incorporates the display data channel (DDC(trademark)) standard. The DDC(trademark) communication channel standard, also proposed by VESA(trademark), defines a communications standard by which a computer system having a monitor may exchange device-specific information among the computer and the monitor using bus lines according to a predetermined protocol. Descriptions of the DDC(trademark) communication channel standard, the EDID(trademark) standard and the E-EDID(trademark) standard are available from the Video Electronics Standards Association (VESA(trademark)) located in Milpitas, Calif. EDID(trademark) data transmitted over a DDC(trademark) channel can be accessed by an external controller.
Typically, monitor initialization for single-interface display monitors is done during each execution of the computer system""s power on self test (POST) procedure and also when a xe2x80x9chot plug-inxe2x80x9d occurs. A hot plug-in occurs when a monitor is plugged into the computer system after the system is already powered up and running. A hot plug-in could occur, for instance, when a monitor is unplugged and then re-plugged while the computer is powered up.
During display monitor initialization, the computer system submits a request for EDID(trademark) file to the display monitor. In the preferred embodiment, the request for EDID file includes a clock signal, SCL, and a data signal, SDA. Upon receiving the request, the monitor transitions from a wait state and relays the EDID(trademark) file to the computer system at the appropriate clock interval. The EDID(trademark) file defines the display monitor""s name as well as the display monitor""s unique properties such as interface type, timing, capabilities, color parameters, and other pertinent information as set forth in the EDID(trademark) standard. Based upon the information relayed from the display monitor to the computer system in the EDID(trademark) file, the computer system can generate the proper initialization process for the display monitor, and can generate the correct video signals, timings, colors and other parameters for transmission to the display monitor.
The typical approach of using a single EDID(trademark) file to be transmitted to the computer system by the display monitor is inadequate for correctly identifying and initializing dual-interface display monitors that include both an analog and a digital interface. Under this approach, the computer system will only recognize one or the other of the display monitor""s two interfaces, but not both. This inadequacy is further augmented by the practical limitation that, under a generally accepted approach for initializing display monitors, once a display monitor product identification code is read by the system from the EDID(trademark) file, the computer system""s registry is loaded with the information from the EDID(trademark) file and no further changes to that portion of the registry file can be made under the same display monitor product identification code.
The present invention employs two unique identification files associated with the same dual-interface display monitor. Each identification file identifies one of the display monitor""s two interfaces, so that each identification file identifies the display monitor as a separate display monitor, with associated characteristics, to the computer system.
In one embodiment, a method for communicating monitor identification information between a dual-interface monitor and a host computer system is disclosed. The method senses whether an initiating event has occurred. The initiating event can be a power on self test. In an alternative embodiment, the initiating event can be a hot plug-in. In another alternative embodiment, the initiating event can be a reboot.
After the initiating event is detected, a request for identification information is provided to the monitor. In at least one embodiment, this identification request includes a clock signal and a data signal.
The method determines whether both an analog video connector and a digital video connector are connected to the monitor. If so, a default identification file is selected. In at least one embodiment, the default identification file is the digital identification file. The default identification file is provided to the host computer system. If both connectors are not connected to the monitor, then the identification file associated with the active connector (i.e., the connector that is connected to the monitor) is provided to the host computer system.
In at least one embodiment, a product identification code that is included in the identification file (either the default identification file of the particular identification file, depending on which one is provided to the host computer system) is used as an index into a database, the product identification code pointing to an information file associated with the monitor.
In one embodiment, the identification file provided to the host computer system is an EDID(trademark) file. In another embodiment, the identification file is an E-EDID(trademark) file.
The identification files include, in at least one embodiment, a video input definition. The video input definition is used to determine whether the dual-interface monitor should receive analog video input or digital video input.
A computer system that supports the communication of identification information between a host system and a dual-interface monitor comprises a processor, a main memory coupled to the processor, an analog video connector, a digital video connector, a dual-interface monitor, and a program code that is stored in the memory and executable by the processor. The code includes instructions for sensing an initiating event, provided a request for identification information from the monitor, receiving the identification file, and using a video input field within the identification file to determine whether the monitor should receive analog video input or digital video input. In one embodiment, the identification file is and EDID(trademark) file. In an alternative embodiment, the identification is an E-EDID(trademark) file. In a further embodiment, the program code includes instructions for using a product identification code within the identification file as a pointer to an information file corresponding to the monitor.
The monitor included in the computer system includes logic for receiving the request for identification file, determining whether both the analog video connector and digital video connector are connected to the monitor, and providing to the processor a default identification file if both connectors are connected. In at least one embodiment, the default identification file is the digital identification file. In at least one embodiment, default identification file may be an EDID(trademark) file. In an alternative embodiment, the default identification file is an E-EDID(trademark) file. The monitor includes logic for providing, if one but not both connectors are connected, an identification file associated with the connector that is connected. Again, the identification file may be an EDID(trademark) file and may also be an E-EDID(trademark) file.
A computer-readable medium embodying the program code described above may, in various embodiments, include a magnetic storage medium, optical storage medium, nonvolatile storage medium, a volatile storage medium, and a data transmission medium.
An apparatus that supports communication of identification information from a dual-interface monitor includes a means for sensing whether an initiating event has occurred, a means for providing a request for identification to a dual-interface monitor, a means for receiving the identification file, and a means for using a video input definition to determine whether the monitor should receive analog video input or digital video input. In at least one embodiment, the apparatus further includes a means for using a product identification code to point to an information file associated with the monitor. In at least one embodiment the apparatus further includes a means for determining whether the monitor is connected to both the analog and digital video connectors, and, if so, for choosing a default identification file and providing the default identification file to a computer system. In at least one embodiment, the apparatus further includes a means of providing the analog identification file to the computer system if the monitor is connected to the analog video connector (but not the digital connector) and for providing the digital identification file if the monitor is connected to the digital video connector (but not the analog video connector). In at least one embodiment, the default identification file, the particular identification file, the analog identification file, and the digital identification file comprise EDID(trademark) files. In another embodiment, they comprise E-EDID(trademark) files. The initiating event may be, in alternative embodiments, a power on self test, a hot plug-in, and a reboot.